Fitting a HEI Module in Transistor Ignition Unit 1977 280Z

[HusseinHolland]

7 minutes ago, Zed Head said:

I completely overlooked what you were saying about the test light on the coil while the engine is running.  The test light passes current so would not give a clean "break" of the coil primary circuit.  The magnetic field collapse would be messed up.  Not sure exactly how.  Surprised the engine didn't just stop sparking, actually.  Make and break is the key to create spark.

Thing is, Volvo and Fiat used similar primitive ignition systems in the 70's & 80's, and with those, one can check ign. pulse with a test light anywhere on the (-) side of the coil circuit, up to the tach & get a flashing lamp without impacting the system. I don't understand why it is differ on the Nissan, however if you're saying that is normal for this system, I won't look any further into it.

 

I can try the stock Nissan condensor on the (-) side also.

Edited October 29, 2023 by HusseinHolland

[HusseinHolland]

Volvo suppressor is 220uF

only holds continuity for a moment, as you intimated, then goes open

 I made a few plugin resistors in the 5-5.5k range to test

[Zed Head]

I can't remember the numbers from the capacitor I used.  Pretty sure I checked once, but it was more to give my meter a workout and to make sure the capacitor was capacitating.  You might compare to the stock Nissan capacitor on the postive side.  Just to see if the numbers are similar since an old Nissan capacitor had worked for me.

Another factor might be that the Nissan tachometers are kind of finicky.  What worked on my tachometer might not work on your tachometer.  Nissan tachs die in a variety of ways.  The one in my 76 was from a 78 parts car.  The 76 unit stopped working when it got hot.

But, adding resistance seems like a good idea.  I'd guess that stronger spark generates stronger kickback.  The factory resistor is something like 2.1 or 2.6 kilo ohms, so add accordingly. You're in the 5's, that might be too much.

Edited October 30, 2023 by Zed Head
+ like

[HusseinHolland]

8 hours ago, Zed Head said:

I can't remember the numbers from the capacitor I used.  Pretty sure I checked once, but it was more to give my meter a workout and to make sure the capacitor was capacitating.  You might compare to the stock Nissan capacitor on the postive side.  Just to see if the numbers are similar since an old Nissan capacitor had worked for me.

Another factor might be that the Nissan tachometers are kind of finicky.  What worked on my tachometer might not work on your tachometer.  Nissan tachs die in a variety of ways.  The one in my 76 was from a 78 parts car.  The 76 unit stopped working when it got hot.

But, adding resistance seems like a good idea.  I'd guess that stronger spark generates stronger kickback.  The factory resistor is something like 2.1 or 2.6 kilo ohms, so add accordingly. You're in the 5's, that might be too much.

Thanks for the response.

I can check the factory cap. Understood, there are permutations & variances with the tachometers. My resistor is 2.23K ohms, the other poster got his to work using 5K ohm range values, which was my guide. Hopefully the rain will stop at some point today, and I can try this tomorrow after work :)

[HusseinHolland]

OK - so finally had the time & break in the weather to swap out the coil & module.

I did first just plug in the HEI module with the stock coil & ballast, and as expected the tach functioned normally with the stock 2.2K ohm resistor.

I swapped out the coil and ballast bridge, and tried the 5K ohm resistor bridge. Tach operated briefly, then dropped. I then added a 1K resistor in series with the 5K, and that was better, but tach was still erratic & dropped out after a bit. Added another 10K (9.8K actual, thought I was adding .5K ohm) and with that, the tach smoothed out, held normal idle rpm & revved freely in time with the engine. So, for me, 15800 ohms is the value required.

I drove the car to work this evening for my parent-teacher conferences, and I have noticed that there is a noticeable 'jerkiness' on throttle tip-in that is not present with the stock ignition setup. Not sure why that would be, I'll have to see if it persists. I also have not swapped out the generic Standard Motor Part module for the geniune GM module, so it is possible that is the culprit I suppose.

Used a 14.8K & 1K in series for the final resistor. 

 

Edited November 2, 2023 by HusseinHolland
correction

[Zed Head]

15,800 ohms.  About seven times the factory number.  Interesting.  I wonder what  the working then dropping out is all about.  Maybe one of the electronics-oriented guy knows.

[Yarb]

@SteveJcould probably give a better answer but it’s current limiting and possibly a voltage drop.

[SteveJ]

First off, let's verify. Did you swap out the guts of the tach with a Volvo tach? 😉

Increasing the impedance in the tach circuit to get it to work is rather puzzling. I'm wondering if a diode in the circuit would accomplish the same thing. That would indicate there is a large voltage spike on coil discharge. The best way to verify would be to use an oscilloscope. (Thanks to @Captain Obvious for pointing me to videos on checking the ignition with a scope.) To be sure, check the coil wire and all of the plug wires to see if they are fully seated in the wells of the coil and distributor cap, especially the coil wire.

I would try to run the car without the tach to see if the tip-in issue would go away. I'm thinking that could be more of a fuel pressure issue than ignition. I have seen something similar on a car I was working on that was too rich because of the FPR setup. It would bog on tip-in and catch quickly. I could see the AFR reading dancing at tip-in.

[HusseinHolland]

21 minutes ago, SteveJ said:

First off, let's verify. Did you swap out the guts of the tach with a Volvo tach? 😉

Increasing the impedance in the tach circuit to get it to work is rather puzzling. I'm wondering if a diode in the circuit would accomplish the same thing. That would indicate there is a large voltage spike on coil discharge. The best way to verify would be to use an oscilloscope. (Thanks to @Captain Obvious for pointing me to videos on checking the ignition with a scope.) To be sure, check the coil wire and all of the plug wires to see if they are fully seated in the wells of the coil and distributor cap, especially the coil wire.

I would try to run the car without the tach to see if the tip-in issue would go away. I'm thinking that could be more of a fuel pressure issue than ignition. I have seen something similar on a car I was working on that was too rich because of the FPR setup. It would bog on tip-in and catch quickly. I could see the AFR reading dancing at tip-in.

No, Factory tach 🙂

I drove the car 15 miles round trip with no tach when I first swapped the HEI module / 12V coil back on Saturday. It was jerky then, I assumed at the time it was because the tank was very low. I don't think it's fuel related, as the symptom does not exist with the stock module & coil setup, it only happened with the HEI setup. It's not a bog, it's definitely a 'cut'. I'll try to observe the wideband controller next time.

All ignition connections are firm. The thing is, I did not experience it driving to work an hour ago. I should recheck the ignition timing in case there is a deviation with the HEI, I think someone mentioned that happened for them.

What is currently annoying is the heat soak 10-15min restart lean condition, it's still happening even though it's now in the 30-50 degree ambient temp weather. I'm looking at alternative fuel rails, which may mean I want to got to composite injectors with the adaptor bases from Protunerz. Not sure I want to go down that rabbit hole though. Maybe I'll just pop the hood latch to vent it if I know I'm going to be in that situation 🤪

Edited November 2, 2023 by HusseinHolland

[SteveJ]

For the heat soak, you may want to try something like this: https://www.amazon.com/gp/product/B000E267JC

[HusseinHolland]

2 hours ago, SteveJ said:

For the heat soak, you may want to try something like this: https://www.amazon.com/gp/product/B000E267JC

I was considering the hose & heat wrap treatment - I think I read FastWoman had put hose over her rail lines & did not experience the heat soak/restart issue. I do have lengths of various DEI wrap, I have used it in the past.

I was also considering making heatshields for the injectors, that would sit over where the exhaust flange is exposed.

Probably better to start with those before going to new rail/injector setup.

Edited November 2, 2023 by HusseinHolland

[HusseinHolland]

OK - so on the drive home from work this afternoon I drove it pretty hard - higher rpm shifts, kept it in 3rd for longer, and drove at higher speed than normal. The engine does feel more 'crisp' & responsive with the HEI module - BUT - it started breaking up much worse on the last leg of my highway run, had to back off the throttle, and it still kept clipping/dropping out. I'm assuming it's the bootleg brand module, so I took the time to swap it out for the GM one. I found that to access that area of the relay panel, the glovebox had to come out, so I decided to relocate the module where I could access it more readily. If the problem persists, I'll just switch back to the stock ignition system.

 

 

Edited November 3, 2023 by HusseinHolland